Disclosed in JP1993-322921A is a technique which performs a self-diagnosis of an electrostatic capacitive sensor having a movable electrode and a fixed electrode arranged to face each other, by applying an electrostatic force to the sensor to simulate deformation and vibration of the structure of the sensor resulting from a certain physical quantity so as to determine whether the sensor normally operates.
Also disclosed in JP2003-121457A is a technique which performs a self-diagnosis of a resonance-based capacitive (electrostatic capacitive) sensor by a measurement using a frequency higher than a resonant frequency to accurately carry out the self-diagnosis by avoiding an abrupt variation in sensor value (measured value) resulting from resonance.